Chiral light from an emitter coupled to an achiral particle via the Purcell effect

TL;DR

This paper shows that non-chiral nanoparticles can emit chiral light when coupled with point emitters under specific conditions, using the Purcell effect and plasmon modes, with experimental validation using gold nanorods.

Contribution

It introduces a method to generate chiral light from achiral particles via emitter coupling and demonstrates this experimentally with electron beam-induced luminescence.

Findings

Non-chiral nanoparticles can produce chiral emission.

Coupling with emitters under the Purcell regime enhances chiral light.

Experimental evidence using gold nanorods confirms the effect.

Abstract

We demonstrate that non-chiral nanoparticles can produce chiral light when point emitters are coupled to their surface plasmon modes (SPMs) under certain conditions. Chiral emission arises from asymmetrical plasmon mode propagation from the source combined with the spin-momentum locked nature of the SPMs. The Purcell regime of cavity quantum electrodynamics (QED) ensures that radiation from the coupled mode dominates over that from the emitter itself, giving rise to photons with a circularly polarized component -- i.e. chiral light. We experimentally demonstrate this effect using electron beam-induced cathode luminescence from a gold nanorod, coupling it evanescently to a nanofiber probe which also supports spin-momentum locked light. This converts the net spin of the emission into a net directionality of propagation in the fiber modes.